Filter unit and process of making same



2106. COMPOSITIONS, COATING 0R PLASTQ oen 24,` 1944.

mwa; nLrLKtNUI; Ummm c. G. GILBERT Erm. 2,361,092

FILTER UNIT, AND PROCESS OF MAKING SAME Filed Jan. 25, 1941 106. CoMPosmoNS,

c Aims R PLASTIG 7 50 2 ent in an amount sufficient to provide body strength against the oil pressures to be encountered but insunicient to render the components stony or non-adsorptive to carbon particles, and the density of pack of the masses in the unitary body being suinciently loose to permit free flow of the oil together with its associated impurities and being equivalent to from 0.12 ounce to 0.24 ounce of the treated material per one cu. in.

Inasmuch as one of the main functions of the gel is to impart rigidity to the cellulose form Without destroying the porosity, the ratio of gel tocellulose necessarily varies with' the type and texture of the paper or other cellulose form and also with the form of gel employed. Accordingly, the ratio of gel to brous material necessarily takes in a wide range. The proportion of adsorbent mineral .gel in the final prod- CROSS REFERENCE 2,361,092 "il rf order that the desirable adherence is insured.

uct ranges between 30% and '75% by weight in the case of corduroyed cellulose wadding and between 5% and 35% by weight in the case of cotton waste.

In its specific embodiment, the filtering medium of the invention consists essentially in a mass of cuttings of corduroyed cellulosic wadding which have been somewhat stiffened with an oilwettable and structurally porous adsorptive minvalong spaced lines or at spaced points, this spaced point compression embossing of the laminated sheet serving to "tack the plies together sufficiently to maintain the plies together during handling. The term specifically excludes papers such as printing and writing and wrapping grades of paper.

By the expression cuttings is here meant strands or small bits severed from the corduroyed cellulosic wadding aforesaid by a shearing operation (e. g., severed by means of shears or knives), and having relatively sharply defined edges the For preparing the filtering agent from the aforesaid wadding, it is preferred to proceed as follows: The cuttings of corduroyed cellulose wadding are, as uniformly as possible, treated Ywith a solution or liquid preparation of water glass or an alumium salt (e. g., the sulphate or the chloride) from which the ultimate stiiener can be produced by reaction of said chemical with a suitable reactant, care being .taken to minimize the messing or pulping of the cuttings. The sotreated cuttings are then subjected to a mild yet thorough treatment with a chemical (e. g., dilute hydrochloric acid in the case of water glass, or ammonia in the case of the aluminum salt) adapted to react with the chemical used as the impregnant .to produce, in and among the bers of the cuttings, an insoluble precipitate of the desired colloid gel. 'Ihe reaction may, in general, be effected by showering or sprinkling the impregnated cuttings onto the surface of a body of liquid containing the suitable reactant and allowing them freely to settle through the body of liquid and to remain `in contact with the latter for a suitable period of time. Thereafter, the cuttings are separated from the liquid, washed with water, dried and thermally conditioned.

In treating the cuttings with thechemical in liquid state, it is preferred to sprinkle or atomize expression specifically excludes shreds, or small I aluminum hydroxide gel, silica gel, or the like,

produced in situ in the clippings. The stiening component: (1) adheres well to the fibers of the clippings so that no-or only an innnitesimal amount of-movement of solids from the filter mass into the oil stream takes place; (2) protects the fibers of the clippings from water, preventing the pulping down of the same; (3) provides a strengthening structure within the clippings,

the liquid by portions -onto a .mass of the cuttings, while continuously turning over the mass of the cuttings to present untreated surfaces to the spray or mist of treating liquid. In this way the cuttings can be made vto take up the desired amount Vof chemical without'becoming mushy and without losing their identity as separate objects. By showering the treated cuttings onto the surface of a bodyof liquid containing the reactant and allowing th'e cuttings to settle freely therethrough it has been found that the desired reaction takes place throughout the whole cutting but that the cutting does not fall to pulp or become altered as to its structure or shape or apparent volume.

, In forming a filter unit from the so-prepared filtering material, the latter is packed into a foraminous basket or container,`under a pressure which is a function of theoil pressure to which the lter unit is to be 'subjected use, viz., under a pressure of 15 "to 20pounds perv square inch in the case of a lter unit adapted for use in the lubricating oil system of an automobile engine operating under 'a 15-20 pound pressure. In the latter case, this pack gives in use about a five-pound pressure drop to the circulated lubricating oil. Were the compression ofthe filtering material to exceed materiallythe working presy sure ofthe oil, the nltering emc'iency of the nlter whereby the combination is able to withstand the varying compressive force of the oil without substantial 'diminution in apparent volume; and (4) more importantly, itself contributes to the filtration by functioning as an adsorbent for acids and other undesirables to be found in the lubricating oil during use of the latter.

unit would be .depreciated because of unnecessary compression and breaking down of the structures. The foraminous container -chosen for this service one which cooperates with the particular oil lter casing lin whichthe same is to be employed. Preferably 'the foraminous container is '75 in the form of'a 'cylinder having imperforate top Examine acerco:

Ezmple I Onto 100 parts by weight of cellulose wedding clippings there was gradually sprinkled an amount of dilute wateaslassiliimiieldlmts (diy weight) nsiueaggl, the clippings being continuously lifted and moved about (tedded) throughout the period of application of the water glass. The impregnated clippings were then sprinkled upon the surface of a body of an aqueous solution of mineral acid (dilute hydrochloric acid, 1 part commercial HC1 to about 7parts of water) through which they fell freely and in which they were allowed to remain for a ripening period. Thereafter, the clippings were removed from the acid solution, were washed free from acid, were dried, and iinally were subjected to a baking treatment at about 105 C.

The baking could have been expedited by employing higher temperature but the strength of ef the wedding hadrnotbeim subiected either to strong'acid ;or strung This product =was an improvement over tthe .product nf Example :I fromthe standpoint orastnxess ci the precipitate.

as will be `understood, gthe upper and lower limits of addition of stiiening agent vare dependent :upon the character of the rbrous cellulosic material ;(cotton waste, cellulose wadding cuttings, and equivalents) employed, :and upon theconditions'to be encountered in any particul lar relation. As a general rule, the more Yopen the fibers of the cuttings would to some extent have been weakened.

The baked product has the appearance and physical properties of the original (untreated) cuttings: the individual strands are flexible and pliable; the fibrous structure is intact; and the apparent volume is the same. However, the baked product does not (as does the untreated material) beanie m`ushy or lose apparent volume after considerable contact with water-containing lubricating oil under pressure.

Example 1r A readily sprayable aqueous solution of water glass was sprayed onto cuttings of corduroyed cellulose wadding, by portions, with continuous tedding of the cuttings, the total amount of solution used being suiiicient ultimately to develop 5 ounces of silica gel per l pound (dry weight) of cuttings. showered upon the surface of, and allowed freely to settle through, a body of reactant solution prepared as follows: 'I'he sodium content of the above impregnating agent was determined, Aand its chemical (that is, reactive) equivalent of aluminum sulphate was calculated; an amount of aluminum sulphate corresponding to a slight excess over that equivalent amount was dissolved in enough water to provide a body of solution of sufcient volume to immerse the volume of impregnated cuttings. The cuttings were allowed to remain in the aluminum sulphate solution for about 15 minutes, after which time they were removed from the bath, drained, washed with a weak aqueous solution of ammonium hydroxide, washed with water until the washings showed no test for alkali, dried, and baked at about 105 C.

As a result of this treatment, silica gel and alu mina gel were homogeneously co-precipitated in amounts to develop 6 ounces of total mineral gel per 1 pound of cuttings (that is to say, 5 ounces of silica gel and 1 ounce of alumina gel). 'I'he practical results included the following: The treated product was physically stronger than was the product from Example I, because the bers The so-impregnated cuttings were the structure for the :dbrous'llulosic material the higher the :percentage of lstiffening :agent should be added. The upper limit, lin practice, may be the limit of holding rcapacity (i. Je., retention of stiiening agent) .of the wadding cuttings-or equivalent-'while the practical llower limit is the point equivalent to pulpingor permanent densication of the .composite structure.

In the case of the product'typifled by Example I, the operable range of stiiening agent lies between about 30% -and about 75%, with the optimum at about 50% by weight. 1n the case of the product typified by Example iII, lthe range of stiffening agent is between 10% and 40% by weight of silica gel, with the percentage of alumina gel being afunctioniofthe silica gel: broadly considered, the combined gels are present in an amount between about 12% and 50% by weight of the total weight of the dried product.

The product of the present invention is sharply distinguished from compositions consisting essentially of cellulcsic bers commingled with preformed stiffening agents such as kaolin, paper clay, bauxita'barium (or calcium, or lead) sulphate, and the like, in a number of respects including adherence of the stiiening agent to the bers. Thus, it has'been :found that the bers of cuttings from sheeted "waterleaf paper containing a loading of vkaolin (or .paper clay, or bauxite) added to the beaten pulp from which the waterleaf paper was formed are not protected against water, and that such cuttings promptly become pulpy and permanently densified when held in contact with oil containing water; moreover, such cuttings lose their loading of stiffening agent to the oil dln'ing use.

The treatments .of 'cellulose wadding described under Examples I and II above improve both the rate and the extent oi.' clean up of fouled lubri cating oil at least about ten fold. Thus, with the lter material of the present invention one can purify in 2 hours fan amount of fouled oil which the untreated wadding per se would require 20 hours to pass, and with better clean up.

"Aspecic iilter unit, using thetreated cuttings above described, particularly adapted for use'in the recirculatory lubricating oil system of a pleasure automobile was constituted as follows, reference being had to the appended drawing: 'I'he container l was aperforated can 4.25 inches tall and 4.25 inches in diameterfprovided with an axially disposed `perforated core 2, which was 0.75 inch in diameter. 'Into the space 3 between core and peripherythere were packed 8.75 ounces of the product of Example I above, under a compression of about S15 pounds per square inch. This unit Awas so arranged in an automobile iilter having a conventional inlet l in the center of the bottom thereof,that said iilter inlet communicated with the interior space of the core of the unit. At'pressures normalto automobile engine systems (15 to 20 pounds gauge), there was obtained `a. .owfthroughhis wicking, at normal cRoss REFERENCE trimm los. commsmows.

comme oR PLASTlC working temperatures (175 C.) -of approximately 1 quart per minute, with a pressure drop of about 5 pounds. After exhaustion of the packing of this unit the latter was inspected; it was found that the entire mass (of filling) was relatively uniformly polluted with 'sludge and assoelated impurities.

A substantial increase .in the density of the packed material (e. g., 12 ounces of the material in the space defined) gave an initial pressure drop of about 8 pounds at the requisite now of 1 quart per minute, which pressure drop shortly increased to 10, 12, 15 pounds, and to a point where no lubricating oil passed through the filtering mateproportioned Eg silica gel, the reac 10 to su e complete neutrality of the silica gel so precipitated, maintaining the so-treated bodies in contact with the solution of reactive chemical until the silica gel has formed, and thereafter separating the so-treated bodies from the rial. Inspection of the too densely packed unit solution, washing them with water and thermalshowed that the entrant surface layer of the ll- 1y conditioning them. ing was thickly coated with s1udge while the re- 2- Process for improving the ltering propermainder of the body of lling contained little or ties of cellulose wedding cuttings Which comno sludge (or other impurities), thus indicating prises mpregnatng Athe cuttings with a solution that there had been but little penetration of of sodium silicate, while continuously loosening sludge into the body of lling. and mixing the cuttings during gradual applica- It was found that if the lling was reduced tion thereto of the impregnating solution, thereto v'I ounces (instead of 8.75 ozs.), the pressure after adding the impregnated cuttings to a body drop was much lower (only about l pound); of a solution of mineral acid, the acid content at the outset of use, rapid filtration (pick-up of of said solution' being adapted completely to resludge) was had, but thereafter there was inact with all the sodium silicate in the cuttings complete filtration and fouled oil passed through' the filling without color change. l ers o n cuttin maintaining These circumstances establish that the present -e cu il: 1n contact w1 the latter solution invention relies upon surface phenomena of the until the silica gel has formed, separating the mineral gel-carrying flbrous material rather than cuttings from the latter solution and Washing upon a mechanical screening effect. them with water, and thermally conditioning the Illustrative of a filter unit found to be oper- Washed cuttings. able in an airplane engine is the following; The 3. A filtering medium for use in the filtration container was a cylindrical can 9 inches in diam- 35 of lubricating oils, Which comprises s resilient eter and 10 inches tall with perforated outer wall assemblage of a multitude of relatively thin and and anaxially disposed perforated core 2 inches narrow, Promscuously arranged disconnected in diameter, and contained about 108 ounces of Worm-like bodies. seid bodies being comprised of the product of Example 1 The direction of now loosely associated cellulosic fibers, each of said was radially outward from the central core space. 40 worm-like bodies containing a siliceous adsorbent The working pressure of the airplane engine on stffenng agent dispersed among the fibers therewl-noh n, was tested was 20 pounds gauge, and the of and tenaciously adhering to the surfaces of rote of now was 2 gallons per minuto, lThe test the latter, the silicon content of said stiifening run lasted '75 hours, in three periods of 25 hours agent consisting of structurally porous neutral each, in the first, of which the lter was oonadsorbent silica gel, said resilient assemblage benected into the recirculatory system, in the secing compacted to a bulk density providing not ond the alter was disconnected, and m the third more than s relatively small drop in the presthe lter was connected into the reirculabory Sure maintained Oll Said circulated lubricating systenn Al, one stan, of the test one lum-lontoil consistent with free flow of the latter through ing oil was new" but had flushed some residual 5.0 the interstices among the compacted bodies consludge (0.12% by weight) from the engine parts. Stitul'liug said resilient assemblage. The filter quickly removed residual sludge from 4. A filtering medium for use in the filtration the circulated oil to a 0.02% content, and hold of oils, which comprises a resilient assemblage the sludge content at between 0.02% and 0.05% 0f a multitude of releliyely thin and no-I'IOW, for the nrst 25 hour run A1; the end of the 65 promiscuously arranged disconnected worm-like second 25 hour run the sludge content of the oil bodies Said bodes being comprised of loosely had increased to 0,30%. In the third 25 honrassociated cellulosic fibers, each of said wormrnn the nlter unit decreased the sludge content like bodies containing a siliceous adsorbent stiffof the circulated oil to, and held the same, not ening agent dispersed among the bers thereof to exceed 0.06% by weight untn the end of the oo and tenaoiously adhering to the surfaces of the run. latter, the silicon content of said stiffening agent It will be appreciated that since the oil was consisting of structurally porous neutral adsorbcontinuously generating sludge, it necessarily ,ent slice gel in an amount corresponding to showed, at best, a certain minimum sludge confrom about 30% t0 about '75% by Weight of the tent equivalent to, say, Go2-0.03% by weight, 65 dry weight of said assemblage, said resilient as- It is to be appreciated also, that use of the lter semblage being compacted to a bulk Weight of unit maintained the sludge content of the oil at from 0.12 to 0.24 ounce per cubic inch and hava value well below that critical point (in this 111g macroscopic tortuous lnterstices among the instance, a calculated value of 0,15%) at which bodies constituting said assemblage for free now sludge would have begun to aggregate and to exof oil therethrough. ercise its carbon-building, and other ill effects.I 5- A lter unit adapted to be installed in a nl- We olonn; ter casing of a recirculating lubricating oil sys- 1. Process for producing a ltering masa-which tem of on internal combustion engine which syscomprises impregnating bodies of loosely associtem includes on oil pump, a pressure oil line, a ated cellulosic fibers with `a solution consisting Casing of on oil llel interposed in the Pressure oil line, and a return oil line from the lter., said lter unit comprising a container having imperforate top and bottom, a oraminous peripheral wall and a foraminous central core dening a central open space for introduction of oil from the pressure oil line, said foraminous peripheral wall, .foraminous core, imperforate top and imperforate bottom dening therebetween a space lled with a, resilient assemblage of a multitude of relatively thin and narrow, promiscuously arranged, disconnected worm-like bodies, said bodies being comprised of loosely associated eellulosic bers, each of said worm-like bodies containing a siliceous adsorbent stifening agent dispersed among the bers thereof and tenaciously adhering to the surfaces of the latter, the silicon content of said stiffening agent consisting of structurally porous neutral adsorbent silica gel in an amount corresponding to from about to about by weight of the dry Weight of the assemblage, the degree of compaction of the assemblage being such as to provide macroscopic tortuous interstices among the bodies constituting said assemblage for free flow of oil under pressure radially outwardly from said core space through said assemblage interstices and to said return line and equivalent to a density of from 0.12 ounce to 0.24 ounce per cubic inch of said assemblage.

CHESTER. G. GILBERT.

GEOFFREY GILBERT. 

